1. Field of the Invention
The present invention relates to valves used for the handling of hazardous materials, chemicals, and chemical process fluids and the like, wherein a magnetically operated external sliding valve actuator moves a valve stem within a closed walled, sealed bonnet and along a linear path between open flow and closed flow positions.
2. General Background
There are numerous chemical plants, paper manufacturing facilities, and other factories used in the manufacturing of chemicals wherein sliding stem type valves (such as plug, globe, and the like) are used. These commercially available valves include a valve plug member operated by a stem which extends into and through a valve bonnet at a dynamic seal called a packing gland. Any type of leakage through this packing gland is at best only costly and at its worst can create an environmental hazard. These emissions, often called "fugitive emissions" can amount to a substantial environmental problem when numerous valves are leaking at a given facility. Such emissions can also trigger chemical reactions such as the formation of acids, that corrode the valve itself.
A sliding stem-type valve creates a special leakage problem as opposed, for example, to a rotary valve because the stem moves in a fashion which sequentially places the stem externally and internally of the housing during its normal operation. The chemical being conveyed can be moved from the inside of the valve to the exterior thereof, or trash can be carried from outside to the inside via the sliding stem. As an example, if the valve is conveying chlorine, molecules of the chlorine can move externally of the valve housing on the stem and contact free hydrogen in the surrounding air, forming hydrogen chloride. This acid can badly corrode the stem, and accelerate the escape of fugitive emissions.
As a solution to this problem, the present invention provides a method and apparatus that eliminates the dynamic seal of the sliding stem and the packing gland which forms a portion of tens of thousands of valves presently in service in the prior art. The present invention provides a seal which is static rather than dynamic and which can be manufactured as a new O.E.M. valve assembly, or in the form of a "kit" for retrofitting valves in existing service which are plagued with leakage at the stem and packing gland.
Various magnetically driven pump arrangements have been patented. For example, the Okulitch U.S. Pat. No. 2,669,668, entitled "Magnetically Driven Centrifugal Pump" pertains to a pump construction having a magnetic coupling with magnetic attraction between rotors on opposites sides of a dividing wall.
Other patents that relate to the concept of magnetic drives for pumps include, for example, the Barotz U.S. Pat. No. 3,172,364, entitled "Pump"; the McCoy U.S. Pat. No. 3,299,819, entitled "Magnetic Drive"; the Pearson et al. U.S. Pat. No. 3,572,981, entitled "Hermetically Sealed Pump"; the Zimmermann U.S. Pat. No. 3,938,914, entitled "Pump Impeller And Coupling Magnet Structures"; the Miyahara U.S. Pat. No. 3,941,517, entitled "Magnetic Hydraulic Pump"; the Dickinson U.S. Pat. No. 4,266,914, entitled "Magnetic Drive Laboratory Pump"; the McCoy U.S. Pat. No. 3,304,532, entitled "Pump Having Magnetic Drive"; the Hauenstein U.S. Pat. No. 4,645,433, entitled "Sealing Shroud Centrifugal Pump"; and the Mizuno U.S. Pat. No. 4,722,661, entitled "Magnetic-Drive Centrifugal Pump".
Various valve constructions have been patented which use magnetic members in operation of the valve. The Gibson U.S. Pat. No. 3,347,262, entitled "Magnet Actuated Sealed Valve", provides a rotary valve magnetic coupling comprising concentric, annular sleeves which are permanent magnet couplings. The Sherwood U.S. Pat. No. 3,476,355, entitled "Magnetic Valve", uses a valve construction for controlling the flow of air, water, or light fluids, wherein a valve housing is made of insulating material having inlet and outlet portions, and a single moving part in the housing, comprises a freely movable valve closing and an opening disc of magnetic material normally supported by the housing over the valve outlet.
The Ignatjev U.S. Pat. No. 3,625,473, entitled "Permanent Magnet Valve With Magnetic Operator", discloses a valve that includes a valving member which is movable between open and closed positions and which is actuated between those positions by respective interaction and non-interaction of two magnetic fields having axes which are disposed at an angle with respect to one another.
A rotary valve construction is seen in the Gigantino U.S. Pat. No. 3,747,892, entitled "Magnetic Valve", wherein a valve structure having a driving sleeve magnetic is operated by a motor and a driven magnetic coaxial with the driving magnet connected to the valve.
Another rotary valve member is the subject of U.S. Pat. No. 4,304,256, issued to Taiani, entitled "Torque Transmitting Assembly For Rotary Valve Member". The Kah, Jr. U.S. Pat. No. 4,310,023, entitled "Magnetically Actuated Pilot Valve", includes a valve structure for fluid control systems which can direct a fluid pressure for operating a device or it can connect the device to drain. The Vanderlaan U.S. Pat. No. 4,672,992, entitled "Direct Drive Valve-Ball Drive Mechanism", provides a ball-like member which is moved by a rotary force motor using a valve coupling.
A gate valve with a magnetic closure is the subject of U.S. Pat. No. 4,747,577, issued to Dimock, entitled "Gate Valve With Magnetic Closure For Use With Vacuum Equipment". In the Dimock patent, a gate valve is provided for use with evacuable equipment and includes a housing having a pair of aligned ports in opposed walls. A valve seat surrounds one of the ports. A gate gate member is reciprocally translatable by means of a linear actuator in a direction generally normal to the central axis of the valve seat. Magnetic structures are operably associated with the gate and valve for pulling the gate and seat into sealing engagement for closure of the gate valve by exerting a closure force generally parallel to the axis of the valve seat. The linear actuator including a hollow cylinder having a piston movable therein and axially thereof which is magnetically coupled through the walls of the cylinder to an actuator member mechanically coupled to the gate for effecting reciprocal motion thereof.